What is the difference between left join and left outer join in Oracle?
What is the difference between left join and left outer join in Oracle?
There really is no difference between a LEFT JOIN and a LEFT OUTER JOIN. Both versions of the syntax will produce the exact same result in PL/SQL. Some people do recommend including outer in a LEFT JOIN clause so it’s clear that you’re creating an outer join, but that’s entirely optional.
What is the left outer join operation?
A left outer join returns all the values from an inner join plus all values in the left table that do not match to the right table, including rows with NULL (empty) values in the link column.
Does left outer join remove duplicates?
Avoiding Duplicates Again, if we perform a left outer join where date = date, each row from Table 5 will join on to every matching row from Table 4. However, in this case, the join will result in 4 rows of duplicate dates in the joined DataSet (see Table 6).
When would you use left join and when left outer join?
LEFT JOIN / LEFT OUTER JOIN : returns all rows from the left table, even if there are no matches in the right table. RIGHT JOIN / RIGHT OUTER JOIN : returns all rows from the right table, even if there are no matches in the left table.
What is a join in the SQL give proper examples for outer join?
(INNER) JOIN : Returns records that have matching values in both tables. LEFT (OUTER) JOIN : Returns all records from the left table, and the matched records from the right table. RIGHT (OUTER) JOIN : Returns all records from the right table, and the matched records from the left table.
Can LEFT join create duplicates?
We can see that the two rows for “Tissues” in the left table got duplicated – we now have four of them! This is because, when joining on the `product` column, the join condition (or “join-predicate”) is true for multiple rows….Join duplications.
| products | ||
|---|---|---|
| product | price | creation_date_utc |
| Tissues | 3.00 | 2017-08-01 |
What is LEFT OUTER JOIN?
LEFT OUTER JOIN. A LEFT OUTER JOIN is one of the JOIN operations that allow you to specify a join clause. It preserves the unmatched rows from the first (left) table, joining them with a NULL row in the shape of the second (right) table.
What is an outer join?
Outer Joins. Outer joins are used to match rows from two tables. Even if there is no match rows are included. Rows from one of the tables are always included, for the other, when there are no matches, NULL values are included. The series starts with the article Introduction to Database Joins.
What is inner join in Oracle?
Oracle INNER JOIN. What is Inner Join in Oracle? The INNER join is such a join when equijoins and nonequijoins are performed, rows from the source and target tables are matched using a join condition formulated with equality and inequality operators, respectively. These are referred to as inner joins.
What is left outer?
Perform left outer joins. A left outer join is a join in which each element of the first collection is returned, regardless of whether it has any correlated elements in the second collection.